This is a MYTH.
If you’ve bought into the “reading in the dark damages your eyes” myth, you’re not alone. According to a study published in the British Medical Journal in 2007, this cautionary tale is one of the seven medical myths most likely to be believed by doctors! You can safely put that myth to bed—reading in dim light may strain your eyes, blur your vision, and give you a headache, but it causes no permanent damage to your eyesight.
The Dim Light Phenomenon
Your eyes are designed to adjust to different light levels, as evidenced by your eyes’ ability to acclimate to the dark, or the involuntary squint that occurs when you turn on a bright light first thing in the morning.
Your eyes contain two kinds of photoreceptors that respond to light signals: rods and cones. When you read in the dark, these nerve cells amp up their production of light-sensitive chemicals, which register the light, and then send a signal to the brain. Your iris muscles relax, which causes your pupils to enlarge in order to take in as much light as possible.
This process sends conflicting messages to your sight muscles. On the one hand, you’re telling them to relax so that the pupils can grow big and let in light. On the other hand, you’re telling them to contract and focus on the image at hand. Focusing is particularly difficult in the dark because there is not as much contrast between the words and the pages. Your eyes have to work harder in the dark, but a little hard work won’t kill them…it will just cause a bit of strain.
Symptoms of Eye Strain
Because it’s difficult to focus when reading in the dark, your eyes tend to blink less and subsequently get dry and itchy. Eye strain can also manifest as headaches, back and neck pain, blurred vision, and sore or itchy eyeballs. So, will reading in the dark hurt your eyes? In the long term….no, and in the short term, it really just depends on your personal tolerance to the dark.